MOSCOW -- Peter Walton, a former English Premier League referee, thinks Cristiano Ronaldo should have been sent off in Monday's tense World Cup match between Portugal and Iran.

"He cuffed him," Walton said of Ronaldo's elbow into the face of Morteza Pouraliganji late in the group stage game. "It was aggressive and it was a strike to the face and, if I was the man on the field, a strike to the face means he has to go."

Clear enough, right? But here is where it gets a little more complicated. Despite feeling that way, Walton also said that if he had been the video assistant at the match, he would not -- would not -- have done what the VAR in that match did, which was call down to the on-field referee, Enrique Caceres, to come over and have another look.

"I know that seems like I'm sitting on the fence," Walton told ESPN FC in an interview on Monday. "But this is the part that needs to be explained about VAR -- the threshold to get involved has to be far, far higher than if you are the man on the field."

Here's what Walton means: the referee on the field makes whatever decisions he deems to be correct and, in doing so, he uses his own judgment. That is the only factor.

For the official working as VAR, the standard has to be higher. Fans are surely already sick of -- if not confused by -- the phrase "clear and obvious," but that is the level to which an incident needs to rise for the VAR to intervene with what the referee has decided. In some cases -- as with Spain's goal against Morocco which was originally ruled out for offside but overturned when a replay showed the attacker was clearly onside -- it is easy.

In instances like Ronaldo's, however, it is not. And to Walton, those are the circumstances where the VAR has to ask himself a straightforward question: Would just about everyone in a room watching this game see the same thing? If the answer is "yes," call the referee and have him view the replay. If the answer is: "Well, the Iranians would absolutely see it as a red but some neutrals might think a yellow is fine and the Portuguese say play on," then, to Walton, the VAR should stand down and let the referee make his own call.

"The VAR has to be the voice of the masses," Walton said. "Maradona's hand-of-God -- even most Argentines would say, yes, it was a handball. Those are the ones VAR is there for. It's not there so that a second person can officiate the game just as the first person is doing."

Howard Webb, another former referee who handled the 2010 World Cup final and has overseen the introduction of VAR into Major League Soccer, said maintaining that separation is critical to VAR's effectiveness.

Webb raised one of the most-discussed incidents in the group stage as an example: when Sweden's Marcus Berg was through on goal and challenged -- unfairly, according to the Swedish team -- by Germany's Jerome Boateng in one of the more intense matches of the group stage.

Sweden felt Berg should have earned a penalty but the referee, Szymon Marciniak, signaled to play on. Swedish fans howled and many neutral observers were bothered that the play was not even flagged for a review. According to Webb, though, proper protocol was followed: the VAR officials did take a look (as they do with any situation) but did not see a "clear and obvious" error -- it was, like Ronaldo's, debatable -- so there was no reason to call Marciniak to the monitor.

On the other side, Webb said he believes there have been several situations that, in his opinion, were called incorrectly. He cited the game between England and Tunisia in which Harry Kane was hauled to the ground in the penalty area and the referee was unmoved. "That should have been given," Webb said. "To me, it was clear." He similarly thought a red card should have been shown to Aleksander Prijovic of Serbia after he appeared to strike a Costa Rican opponent in the face; the referee in that situation only issued a caution.

Carlos Queiroz, the coach of Iran, went on a lengthy screed about VAR late Monday night, and one point he raised -- that he would like to hear what, specifically, the referee and VAR are looking at during a review -- is something that Walton said is actually a realistic possibility.

In rugby, conversations between the replay official and on-field official can be heard, and Walton said he believes that is "phase two or three" of the VAR experience in football. Allowing those conversations to be public would at least allow coaches and players (and fans) to understand why an official determined what he or she did, and would -- hopefully -- decrease the intensity of protests because of it.

"I do think it has a place in football," Walton said. "I think getting the explanation of how the decision is reached getting out to the masses is so important. At least then, in the situation last night, even if Carlos still disagrees, at least he knows how it was reached."

Sam Borden is a Global Sports Correspondent for ESPN, also covering soccer for ESPN FC. Follow him on Twitter @SamBorden.